In conventional MIMO (Multiple Input Multiple Output) systems, such as FIG. 1 gives one example of conventional MIMO, the eNB (evolved Node B) is mainly optimized to serve UEs (User Equipment) on the ground. In the vertical dimension, the same narrow beam is applied to both data and control. This vertical beam is usually pointing to the UE in the ground which has most of the traffics flows. In the horizontal dimension, the narrow beam is only applied to data. Wide beam is applied to control to ensure its reliability in the targeted coverage area. However, in a 3D-MIMO system, such as an example of 3D-MIMO shown in FIG. 2, the eNB needs to cover UEs both on the ground and on high floors. In order to achieve this target, the eNB uses different vertical beam to serve UEs on different floors. In order to ensure reliable decoding of PDCCH (Physical Downlink Control Channel), using a fixed vertical narrow beam may be risky, especially for the UEs on the high floors. Therefore, the eNB needs to implement a wide vertical beam for PDCCH transmission. This wide vertical beam can patch the coverage holes of PDCCH caused by a narrow vertical beam in the vertical dimension. It also creates reasonable 3D cell coverage for each eNB so that the eNB is able to adjust the vertical narrow beam to transmit data to any UE as long as it is within the 3D coverage area of its PDCCH. But the existing wide beam pattern for control channel transmission in a 3D-MIMO system, such as 3GPP RANI R1-142860, “On cell association in FD-MIMO systems”, it does not have coverage holes for PDCCH transmission in the vertical dimension. But the problem is that the 10-element antenna array gain relative to a single antenna element diminishes. The coverage hole is avoided at the cost of reduced coverage range. Therefore, a scheme is needed that not only can avoid coverage holes in the vertical dimension, but also can enhance the common control channel coverage in a 3D-MIMO system to achieve a certain performance target, such as at least matching that of the 2D-MIMO system.